York County Administrative Center, York, PA
Structural Design & Restoration
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Fig. 1
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Fig. 2
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Fig. 3
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Fig. 4
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Fig. 5
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Fig. 6
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Fig. 7
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Project Background
As part of a $22 million adaptive reuse of the original York County Courthouse, the York County Commissioners authorized the restoration of the original early 1900s structure as the new York County Administrative Center. The project included three terra cotta domes and associated appendages, which were restored using a unique design/restore fast-track approach. The three terra cotta domes were accessed, evaluated, and restored in less than 11 months total.
The project’s general contractor, Wohlsen Construction Company, engaged Noble Preservation Services, Inc. to review the terra cotta domes. Noble Preservation’s preliminary assessment recommended that the County consider assembling an appropriate team to orchestrate a well designed and implemented rehabilitation program to provide long-term solutions to ongoing problems. Subsequently, the project owner authorized the assemblage of a repair and preservation team. Masonry Preservation Services was brought on as a historic masonry restoration contractor.
Project Scope
Following the project’s preservation team’s initial inspection and invasive probes, including recommendations for repairs, recommendations included the following major repair/preservation work items:
Small Domes North & South
- Remove and rebuild the entire terra cotta assemblies, starting at the window head lintels up to and including the band directly below the dome tiles.
- Clean and restore the exposed support steel and provide precast concrete components to replace terra cotta where required.
- Remove glazing and rebuild the skylights to include new copper flashing and sealant joints to interface with the terra cotta ribs. This work also included pre- and post-water testing to prove repair efficacy. (Figs. 1 & 2)
- 100% repointing of mortar joints with an appropriate historic mortar.
- The design and installation of sealant joints including roof tile to dissimilar materials and all non-vertical terra cotta joints, which also included the application of a reinforced membrane application.
- Miscellaneous repairs including the copper dome and finial and new reglet at the roof counter flashing.
- Washing of all masonry surfaces.
- Selectively remove and replace roof tile with new custom terra cotta units.
Main Dome & Bell Cupola (Fig. 3)
- Remove, shore, and rebuild the complete lower belt course and the course directly above, which had been displaced due to advanced oxide jacking of support steel. (Figs. 4 & 5)
- Clean and restore the exposed support steel and provide precast concrete components to replace the original terra cotta. (Fig. 6)
- Re-anchor acroterions.
- Remove glazing and rebuild the skylights to include new copper flashing and sealant joints to interface with the terra cotta ribs.
- Remove the original wind vane and replicate the entire assembly for reinstallation. (Fig. 7)
- Rebuild the entire cupola including shoring and rebuilding of the bell carriage, replacement and reinforcing of the steel superstructure, and replacement of the terra cotta and cast stone with new materials.
- 100% repointing of mortar joints with an appropriate historic mortar.
- Design and installation of sealant joints including roof tile to dissimilar materials and all non-vertical terra cotta joints, which also included the application of a reinforced membrane application.
- New reglet at dome for roof counter flashing.
- Washing of all masonry surfaces.
- Selectively remove and replace roof tile with new custom terra cotta units.
Project Approach
After the owner considered both the time and economic implications of completing the dome restoration program using traditional design/bid/construction methods, a negotiated design/restore option was chosen. MPS completed its work based on a fast-track, not-to-exceed-contract, billed on a time and material basis.
Project Solutions
The original construction of the domes included glazed terra cotta suspended from a steel framed substructure. At numerous locations, the original design did not provide adequate provisions to accommodate sufficient flashing and/or redundant multi-wythe backup masonry to protect the mild steel substructure from wind-driven rain and/or condensation. The resulting corrosion of mild steel caused oxide jacking of displaced terra cotta components, which in turn allowed more moisture to enter the assemblies. Deficiencies in the original design, coupled with misguided maintenance/repair campaigns also contributed to an accelerated deteriorative cycle.
MPS’s repairs were designed to provide maximum sustainability and minimize future maintenance. These repairs included the introduction of new and improved copper flashings at skylights, membrane-protected skyward-facing terra cotta joints, and corrosion-inhibitive coatings applied to all exposed steel substructures. However, as with all historically significant assemblies in service for 100 plus years, MPS recommended that the domes be assessed and reviewed on a maximum five-year basis.
For more information on Masonry Preservation Services, contact us today or call 800-772-3573. |
